U.S. patent application number 16/644228 was filed with the patent office on 2020-07-02 for low viscosity noise attenuating material for automotive trim parts.
This patent application is currently assigned to Autoneum Management AG. The applicant listed for this patent is Autoneum Management AG. Invention is credited to Yann BERGER, Raphael MERRIEN.
Application Number | 20200207965 16/644228 |
Document ID | / |
Family ID | 60042972 |
Filed Date | 2020-07-02 |
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United States Patent
Application |
20200207965 |
Kind Code |
A1 |
BERGER; Yann ; et
al. |
July 2, 2020 |
Low Viscosity Noise Attenuating Material for Automotive Trim
Parts
Abstract
An injection moulded noise attenuating layer for an noise
insulating trim part comprising a thermoplastic elastomeric
material and an inorganic filler content of at least 50% by weight,
preferably between 60 and 85%, based on the final material
composition characterised in that the injection moulded noise
attenuating layer has a melt volume index (MVI) of between 100 and
500 cm.sup.3/10 min, preferably between 150 and 350 cm.sup.3/10
min, more preferably between 175 and 225 cm.sup.3/10 min measured
according to current ISO 1133-1.
Inventors: |
BERGER; Yann; (Aadorf,
CH) ; MERRIEN; Raphael; (Winterthur, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Autoneum Management AG |
Winterthur |
|
CH |
|
|
Assignee: |
Autoneum Management AG
Winterthur
CH
|
Family ID: |
60042972 |
Appl. No.: |
16/644228 |
Filed: |
August 30, 2018 |
PCT Filed: |
August 30, 2018 |
PCT NO: |
PCT/EP2018/073363 |
371 Date: |
March 4, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L 23/14 20130101;
C08L 2207/04 20130101; G10K 11/168 20130101; G10K 11/162 20130101;
C08L 2207/02 20130101; C08L 23/14 20130101; C08L 23/16 20130101;
C08L 23/16 20130101; C08K 2003/3045 20130101; C08L 23/14 20130101;
C08L 23/16 20130101; C08L 23/16 20130101; C08K 2003/265
20130101 |
International
Class: |
C08L 23/14 20060101
C08L023/14; G10K 11/168 20060101 G10K011/168 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 19, 2017 |
EP |
17191798.2 |
Claims
1-13. (canceled)
14. A noise attenuating layer for a noise insulating trim part
comprising: a thermoplastic elastomeric material; and an inorganic
filler content of at least 50% by weight based on the final
material composition, wherein the noise attenuating layer has a
melt volume index (MVI) of between 100 and 500 cm.sup.3/10 min
measured according to current ISO 1133-1.
15. The noise attenuating layer according to claim 14, wherein the
noise attenuating layer has a Young's modulus of between 10 and 80
MPa.
16. The noise attenuating layer according to claim 14, wherein the
thermoplastic elastomeric material comprises at least 7% of a
propylene ethylene copolymer.
17. The noise attenuating layer according to clam 16, wherein the
propylene ethylene copolymer has a random ethylene distribution
with a viscosity at 190.degree. C. of between 7000 and 8000
mPas.
18. The noise attenuating layer according to claim 14, wherein the
thermoplastic elastomeric material comprises at least one of a
partially amorphous polyolefin (component B1) or a reactor based
thermoplastic polyolefin with a melt flow index at 230.degree. C.
of between 17 and 35 g/10 min (component B2) or both B1 and B2.
19. The noise attenuating layer according to claim 18, wherein the
at least one of a partially amorphous polyolefin (component B1) is
an amorphous poly-alpha-olefin.
20. The noise attenuating layer according to claim 19, wherein the
thermoplastic elastomeric material comprises component B1 and B2 in
a weight ratio of 1.2 to 2.0.
21. The noise attenuating layer according claim 14, wherein the
inorganic filler is at least one of Barium Sulphate or Calcium
carbonate.
22. The noise attenuating layer according to claim 14, further
comprising an organic or inorganic oil.
23. The noise attenuating layer according to claim 14, further
comprising at least one of a dye additive, a thermal stability
additive, a flame retardant additive, a miscibility enhancing
additive, and a mold release enhancing additive.
24. An acoustic attenuating trim part for a car comprising: at
least a mass layer; and a decoupling layer, wherein the decoupling
layer is injection molded and comprised of a thermoplastic
elastomeric material and an inorganic filler content of at least
50% by weight based on the final material composition, wherein the
noise attenuating layer has a melt volume index (MVI) of between
100 and 500 cm.sup.3/10 min measured according to current ISO
1133-1.
25. The acoustic attenuating trim part according to claim 24,
wherein the decoupling layer has a variable thickness in the
direction perpendicular to the surface of the material.
26. The acoustic attenuating trim part of claim 14, further
comprising at least one additional layer chosen from an open or
closed cell foam layer, a porous fibrous layer, a scrim layer or
textile layer, wherein the noise attenuating layer is at least
partly injection molded in a recess or recesses of the at least one
addition layer.
27. The acoustic attenuating trim part of claim 26, wherein the
noise attenuating layer is a patch.
28. Method of producing the noise attenuating layer of claim 14,
comprising the steps of: compounding by mixing and heating to
create a molten compound of at least the elastomeric material and
the filler to create a compound with an MVI of at least 100 cm3/10
min; and low pressure injecting the molten compound into a mold to
form the noise attenuating layer.
29. Method according to claim 28, further comprising cooling,
pelletizing, and reheating the compound before low pressure
injecting the molten compound into a mold.
Description
[0001] This application is a national stage application under 35
U.S.C. 371 and claims the benefit of PCT Application No.
PCT/EP2018/073363 having an international filing date of Aug. 30,
2018, which designated the United States, which PCT application
claimed the benefit of European Patent Application No. 17191798.2,
filed Sep. 19, 2017, the disclosure of each of which are
incorporated by reference herein.
TECHNICAL FIELD
[0002] The invention is directed to a noise attenuating material
for an acoustic noise attenuating trim part for a vehicle, the use
of such noise attenuating material in an automotive trim part and
method of producing such a trim part.
BACKGROUND ART
[0003] Noise attenuating automotive trim parts may be based on
different principles like for instance a spring mass concept or a
damping concept. The noise attenuation may be based on the use of
an airtight elastomeric layer eventually filled to increase the
density, for instance to form a mass layer in a mass-spring
acoustic vehicle trim part like an inner dash.
[0004] Examples of such elastomeric layers can be found in for
instance WO 2015/135815 disclosing a barrier layer based on an
ethylene polymer mixture preferably containing LLDPE or LDPE and
with filler content of between 35% and 90%. The material disclosed
can be formed by standard methods, into the thickness and shape
desired. However, the material and current processes do not allow
for thickness variation or the freedom to form a 3D shape.
[0005] The disadvantage of this and comparable materials is the
high viscosity of the material at the temperature the material is
further processed. This increases the pressure necessary for
forming of the final product, increasing the cost of production
machines.
[0006] An alternative way of applying this type of material was
developed as coating solutions that are sprayed directly on the
trim part surface. This enables a variable thickness of material,
but the quality obtained may not rise to the expectations. In
particularly, the drying times are higher, and the process is
complex. Barrier layers for spray formulations may be thermoset
materials based on reacting substances and solutions with more
volatile solvents to decrease drying times.
[0007] Heavy layer, also known as mass or barrier layer, is
generally made of a thermoplastic elastomeric material comprising a
high amount of fillers. These layers may be produced as a sheet
layer through calendaring. The sheets are cut into shape and or
size and formed using a vacuum forming process into the final shape
eventually together with additional layers, like the decoupling
layer. The process of which comprises multiple steps and it is
difficult to achieve variable thickness. Process adjustments to
obtain variable thickness that have been proposed in the past, such
as adding additional patches on top or using an embossing calander,
are still laborious and not efficient.
[0008] One process proposed is the combination of extrusion and
compression molding. As the material composition is still the same
or similar to the one used for the calendared solution the
compression forces needed are high. The combined process of
injecting and compressing is needed to fill the full cavity,
including remote areas and smaller details. Therefore, the material
is pushed during cooling, increasing the risk of streaking and
pairing half solidified areas. These areas may by prone to cracking
or breaking during the molding step of the final part as well as
during the use of the part in the car. The mold is open during
filling and closed later in the process, to increase the pressure
pushing the material to the corner of the form.
[0009] It is the object of the invention to provide for an
alternative noise attenuating layer enabling easier process
conditions, decreasing the cost of production and the wear of the
machines. However, maintaining the requirements of the product,
when used as a barrier in a spring mass acoustic system for an
automotive trim part.
SUMMARY OF INVENTION
[0010] The object of the invention is achieved by a noise
attenuating layer for a noise insulating trim part according to
claim 1.
[0011] In particularly by a noise attenuating layer for an noise
insulating trim part comprising a thermoplastic elastomeric
material and an inorganic filler content of at least 50% by weight,
preferably between 60 and 85%, and based on the final material
composition having an overall melt volume index of between 100 and
300 cm.sup.3/10 min., preferably between 150 and 250 cm.sup.3/10
min., more preferably between 170 and 220 cm.sup.3/10 min. Melt
volume index as measured at 190.degree. C. according to the
ISO1133-1 from 2012.
[0012] The Noise Attenuating Material
[0013] The injection molded noise attenuating material according to
the invention comprises of a thermoplastic elastomeric material
(TEM) and inert filler material (IFM).
[0014] In this application all % are defined as % by weight based
on the total weight of the injection molded noise attenuating layer
unless otherwise specified.
[0015] The inert filler (IFM) is preferably one of Barium Sulphate
(BaSO.sub.4) or Calcium Carbonate (CaCO.sub.3). The Barium Sulphate
filler used preferably has a median particle size d50 of between 20
and 30 micron. While the median particle size d50 for Calcium
carbonate is preferably between 5 and 15 micron.
[0016] The injection molded noise attenuating layer according to
the invention comprises at least 50% by weight, preferably up to
85% by weight of IFM. Depending on the filler content the density
of the final material is set.
[0017] A denser material is preferred as the layer needs less
space. The weight of the mass layer is important for the noise
attenuation, therefore the area weight hence the density can be
used to tune the part.
[0018] Advantageously the viscosity of the material during
production enables a high level of possible variance in the
thickness distribution throughout the part, giving rise to a
variable mass distribution. The variance in mass distribution is an
advantage for the design of the part, having enough mass in the
areas where a high acoustic insulation is needed and having none of
a low mass in those areas where acoustic insulation is not
necessary. The injection mold can even allow for areas without the
noise attenuating material leaving gaps or holes for instance for
areas of pass through, like for instance in the area of the foot
pedals or where cables are going through the part.
[0019] However, the injection molded material can also be made in a
precise thickness due to the closed mold with specified thickness
profile, contrary to the state-of-the-art calendaring methods where
there may be a huge variance in the actual thickness obtained even
if a constant thickness was the aim.
[0020] Preferably the thickness of the injected molded layer is
between 0.7-5 mm, preferably between 1.5-3.5 mm.
[0021] Surprisingly due to the injection molding of the barrier
material having a low MFI it is possible to obtain a very thin and
precise thickness area weight distribution. In particularly it
becomes possible to produce layers in the thickness area weight
requirements more precisely than with state-of-the-art material
process combinations. Even in the lower thickness areas of around 2
to 3 mm, it is possible to stay within a narrow tolerance.
[0022] The thermoplastic elastomeric material (TEM) comprises of a
Component A, at least one component B, and optionally additional
additives.
[0023] Component A consists of a propylene ethylene copolymer,
preferably with a random ethylene distribution, with a viscosity at
190.degree. C. of between 7000 and 8000 mPas, preferably between
7430 and 7800 mPas. Preferably the copolymer used is not a block
polymer. Preferably the injection molded material comprises at
least 7% by weight of component A, preferably between 10 and 25%. A
commercial example of component A may be for instance Vistamaxx
from Exxon.
[0024] Component B consist of at least one of a partially amorphous
polyolefin (Component B1), preferably an amorphous
poly-alpha-olefin, or a reactor based thermoplastic polyolefin with
a melt flow index at 230.degree. C. of between 17 and 35 g/10 min
(Component B2). Preferably component B comprises component B1 and
B2.
[0025] A commercial example of component B1 may be for instance
APAO Vestoplast, while an example for component B2 may be for
instance Adflex.
[0026] Preferably the injection molded material comprises between
2% and 13% by weight of component B, preferably between 4 and
8%.
[0027] Preferably component B comprises of component B1 and B2 in a
ratio of between 1.2 and 2.0 (B1/B2).
[0028] A commercial example of component A may be for instance
Vistamaxx from Exxon.
[0029] TME may further comprise other additives like organic or
inorganic oil, preferably one of paraffin oil or rosin oil. TME may
further comprise at least one of a dye additive, like carbon black,
a thermal stability additive, like a high melt polypropylene, a
flame-retardant additive, a miscibility enhancing additive, or a
mold release enhancing additive.
[0030] Preferably the injection molded material does not comprise
more than 6% by weight of these other additives including
optionally oil.
[0031] Preferably the oil component may be up to 4% by weight of
the injection molded material.
[0032] IFM and TEM form together 100% by weight of the noise
attenuating material according to the invention, having a MVI of
between 100 and 500 cm.sup.3/10 min, preferably of 150 and 350
cm.sup.3/10 min, more preferably 175 and 225 cm.sup.3/10 min. The
thus material formed has preferably a Young's modulus of between 10
and 80 MPa. Preferably combined with a shore hardness of between
70A and 95A.
[0033] Surprisingly the noise attenuating material layer according
to the invention has a low viscosity and still the high required
filler content, giving a material that can be easy processed, and
that is flexible enough to function as an elastomeric layer in for
instance an acoustic mass-spring system, without breaking or
crumbling.
[0034] Furthermore, surprisingly the noise attenuating material
obtained when heated before final injection molding is very liquid
despite the high content of inert filler, however, is able to
provide a flexible and soft enough material to form a stable noise
attenuating layer when used in the car.
[0035] Preferably the noise attenuating material when injection
molded into the final shape in the form of a sheet, layer, patch or
similar (afterwards referred to as layer) to be used in a vehicle
trim part has a melting temperature of at least 80.degree. C.,
preferably at least above 100.degree. C., more preferably above
120.degree. C.
[0036] The noise attenuating material layer according to the
invention may have an area weight of at least 0.5 kg/m.sup.2,
preferably at least 1 kg/m.sup.2. Preferably not more than 10
kg/m.sup.2.
[0037] The density depending on the filler content may be at least
1.3 kg/m.sup.3, preferably not more than 2.5 kg/m.sup.3.
[0038] Trim Part Including the Noise Attenuating Material
[0039] The noise attenuating material according to the invention is
injection molded in a closed mold formed with a first half and a
second half together enclosing a space in the final shape of the
injection molded material layer. This can be in the form of a
layer, patch or sheet in the required form and thickness to be
used. The part formed may be used either as a single layer trim
part, or combined locally or fully on the surface of at least a
second layer to form a noise attenuating trim part.
[0040] A single mold might also include multiple patches together
forming the inlay for a noise attenuating trim part or trim parts.
Preferably injection molded patches, parts or layers might be used
without further treatment or may be trimmed.
[0041] The noise attenuating material can be used on its own for
instance to reduce vibrational damping of a surface, preferably the
material is adhered to the surface of the area to be dampened for
instance by using magnetic means or by applying a glue layer.
Preferably the filler of the noise attenuating material comprises
magnetic inert filler.
[0042] The noise attenuating material may also be used in a trim
part with at least one additional layer. The additional layer is
adhered over substantially its entire surface with the surface of
the noise attenuating layer or patch.
[0043] Preferably, the at least one additional layer is one of a
decoupling layer, fibrous felt layer, foam layer or carpet
system.
[0044] In case the additional layer is a decoupling layer, the
decoupling layer is placed on the surface of the noise attenuating
material layer facing away from the interior of the car. While the
decoupler may be in contact with at least one surface vibrating and
radiating noise. The noise attenuating material will take the
function of a barrier or mass layer in an acoustic mass-spring
insulating system.
[0045] The decoupling layer can be at least one of a fibrous felt
layer or a soft foam layer.
[0046] The fibrous felt layer used as the at least one additional
layer as just defined comprises of a binder and fibers, or fibers
alone. The binder can be any type of material that can melt or cure
during molding and bind the fibers together to form a consolidated
fibrous layer. The binder can be any type of thermoplastic or
thermoset binder, like phenolic or epoxy resin or derivatives of
such resin.
[0047] Alternatively, or additionally the felt layer can be
consolidated by a mechanical process known in the art, for instance
needling.
[0048] The binder can be applied in the form of powder, flakes or
fiber.
[0049] As thermoplastic binder preferably at least one of the
materials selected form the group consisting of polyester,
preferably polyethylene terephthalate, polyolefin, preferably
polypropylene or polyethylene, polylactic acid (PLY) and polyamide
such as polyamide 6 or polyamide 66, or any of their copolymers may
be used.
[0050] For example, as binder a low melt polyester or polyolefin
with a melt point lower than the filler fibers can be used.
Preferably bi-component fibers might be used for instance a core
sheath type of fiber with the sheath forming the binder component
and the core forming the fiber felt material. For instance, a
coPET/PET bicomponent fiber whereby the coPET forms the binder and
the PET forms the fibers within the felt material after
molding.
[0051] Preferably at least 0-50% by weight of the final felt
material is formed by binder, preferably 10-40%, and even more
preferred 20-30% by weight. The binder is preferably applied in the
form of fibers.
[0052] The fibers used might be staple fibers or endless filaments.
If the word fibers is used both staple fibers and endless filaments
are meant except if the type of fibers is explicitly mentioned.
[0053] The fibers comprise at least one of natural fibers, like
cotton, mineral fibers, like glass or basalt fibers, or man-made
fibers, like polyamide (nylon) such as polyamide 6 or polyamide 66,
polyester such as polyethylene terephthalate (PET) or polyolefin
such as polypropylene or polyethylene or mixtures thereof.
[0054] The fibers might come from a virgin, reclaimed or recycled
source, for instance in the form of shoddy material, preferably
shoddy cotton, synthetic shoddy, polyester shoddy or natural fiber
shoddy.
[0055] Reclaimed fibers are preferably produced from textile
fabrics. The shoddy type is defined by having at least 51% by
weight of the material included, 49% can come from other sources.
So, for instance shoddy polyester contains at least 51% by weight
of polyester based materials. Alternatively, the shoddy material
can be a mixture of different synthetic and natural fibers, whereby
not one type is prevailing.
[0056] The fibers may also come from regenerated sources, like for
instance regenerated polyester.
[0057] The fibers used for the at least one additional layer, in
particularly the decoupling layer, may have a solid cross section
or hollow cross section, or a combination of fibers with a hollow
and solid cross section might be used. For instance, to further
enhance the durability and or to obtain a lighter part.
[0058] Surprisingly the use of a combination of fibers including
frizzy fibers for instance hollow conjugate curled fibers further
enhances the loftiness and softness of the decoupling layer and the
acoustic performance of the overall molded floor covering
system.
[0059] In case of staple fibers used for the decoupling layer they
have preferably a fiber length of between 28-76 mm, preferably
between 32-64 mm.
[0060] The fibers--staple fibers or endless filaments, used for the
at least one additional layer, in particularly the decoupling
layer, are preferably between 1.7 and 28 dtex, preferably between 3
and 15 dtex, preferably between 3 and 12 dtex.
[0061] Eventually foam chips might be added to the additional layer
or layers based on fibrous felt. Preferably up to 30%, more
preferably up to 25% of the total area weight of the layer might be
foam chips or shredded foam. Preferably the foam is based on
polyurethane foam, preferably soft polyurethane foam. The density
of the foam used is preferably between 10 and 100 kg/m.sup.3,
preferably between 20 and 90 kg/m.sup.3. The size of the shredded
foam pieces or chips is preferably between 2 and 20 mm, preferably
between 3 and 15 mm.
[0062] Preferably the at least one additional layer has an area
weight of between 80-2500 gm.sup.-2, preferably up to 1200
gm.sup.-2 preferably up to 1000 gm.sup.-2.
[0063] The at least one additional layer after molding might be
having a constant area weight or a constant density. The thickness
and or area weight might also vary over the surface depending on
the final shape and acoustic requirements.
[0064] The fibrous layer might be produced according to known
processes for instance using the process of carding, cross lapping
and needling or the alternative process of air laid and eventually
needling to produce a consolidated fibrous mat the mat can be cut
in blanks to be used in the molding process. Alternatively, the
fibrous material can be directly laid into a mold and consolidated
for instance using the device for molding fibrous material as
disclosed in EP 2640881.
[0065] Also, a standard open cell foam material may be used as the
at least one additional layer according to the invention. The
additional layer may be formed from any type of thermoplastic or
thermosetting foam. Preferably the decoupling layer is made of
polyurethane foam.
[0066] Preferably the foam has a density between 25 to 100
Kg/m.sup.3, preferably 35 to 80 Kg/m.sup.3, preferably 45 to 70
Kg/m.sup.3.
[0067] The additional layer, in particularly if it functions as a
decoupling layer, has preferably a low compression stiffness of
less than 20 kPa, preferably above 4 kPa, preferably between 5 and
15 kPa, preferably between 5 and 10 kPa, measured according to the
current ISO 3386-1. The measured stiffness is the compression
stress value CV40, also called CLD40 value, measured at 40%
compression.
[0068] The foam can be produced in foam blocks and cut in layers
with the right thickness to be molded to the final part.
Alternatively, it may be applied according to the reaction
injection molding process whereby the foam is directly reacting in
the mold forming the final shape. Preferably it is attached to the
thermoplastic elastomeric layer during injection molding of the
foam.
[0069] The thickness and stiffness of the at least one additional
layer, in particularly the decoupling layer, independent of the
material chosen may be optimised to meet acoustic and stiffness
targets as well as overall rigidity requirements of the trim part.
In addition, the thickness is dependent on space restrictions in
the vehicle. Preferably the thickness can be varied over the area
of the part to follow the available space in the vehicle. The
thickness available may vary between 1 and 100 mm but in most cases
the thickness varies between 5 and 40 mm. For instance, typical
overall average thickness of a decoupling layer of a carpet or
inner dash is between 15 and 25 mm, e.g. in average about 20
mm.
[0070] One option is to directly back foam polyurethane against the
noise attenuating layer or against patches using a reaction
injection molding process to form a foam layer adhered to the noise
attenuating layer or patch. The foam may be used as the decoupling
layer or alternatively an open cell foam layer may be functioning
as a noise absorbing layer facing towards the relevant source of
noise. Alternatively, foam is applied on both sides forming an
insulating and absorbing acoustic trim part. For instance, for an
inner or outer dash cladding. The noise attenuating material layer
might have small holes to enable the flow of foam to both sides and
a good bonding of the overall structure.
[0071] The noise attenuating material might be injected directly on
the at least one additional layer, preferably on an additional
layer in the form of fibrous felt or foam as defined before. This
can be on the full surface, as patches on top of the material and
or in predefined recesses in the additional layer.
[0072] Pre-defined recesses can be made during the pre-shaping of
the additional layer.
[0073] Other layers may be placed on the additional layer and or on
the surface opposite the first additional layer, like for instance
layers comparable to the one already defined as additional layer,
or at least one of a film layer, like a single or dual layer film,
scrim layer, or an aesthetic surface layer, like a tufted or
nonwoven carpet or textile, of combinations of such layers.
[0074] Preferably the first additional layer or the additional
layer is a fibrous felt layer with the fibers bound on binding
points with a thermoplastic binder forming a consolidated fibrous
layer. In particularly in the case of back injection molding the
noise attenuating material a consolidated layer is preferred.
[0075] The acoustic attenuating trim part according to the
invention comprising at least the noise attenuating material
comprising a thermoplastic elastomeric material and an inorganic
filler content of at least 50% by weight, preferably between 60 and
85%, and based on the final material composition having an overall
melt volume index of between 100 and 300 cm3/10 min., preferably
between 150 and 250 cm3/10 min., more preferably between 170 and
220 cm3/10 min and at least one additional layer may be used as or
in an inner or outer dash, a petrol or electric engine cover or
side panels, as part of a flooring system, as trim part or cladding
in the trunk, headliner or passenger compartment. Preferably it is
used combined with a decoupling layer of one of a soft foam or
felt, to be used as a mass spring system for noise attenuation, for
instance as an innerdash or flooring system, eventually combined
with deco surface layer, like scrims, nonwoven, needlepunch or
flocked carpets or other types of decorative coverings.
[0076] Process
[0077] A preferred process of the noise attenuating material
according to the invention comprises at least the steps of [0078]
mixing and heating the material mixture comprising at least the
thermoplastic elastomeric material and the inert filler, preferably
until a melt volume index (MVI) of between 100 and 500 cm3/10 min,
preferably between 150 and 350 cm3/10 min, more preferably between
175 and 225 cm3/10 min is obtained; [0079] Injecting the molten
material in a closed mold, optionally directly on an additional
layer or layers like in the form of a pre-shaped fibrous web;
[0080] after at least partly cooling the part removing it from the
mold.
[0081] A compression step is not foreseen, or deemed necessary.
[0082] Due to the low MVI it is possible to fill also a mold with
more intricate shapes without the need for additional pressure to
distribute the material; this has the advantage that thinner walls
can be achieved. Designs with thinner areas are now possible
without the problems related to high pressure and high tonnage.
[0083] The material obtained may be directly formed in the relevant
shape for the acoustic part to be produced. Alternatively, the
material is mixed and formed in pellets which are later fed in an
injection molding machine for injection molding the parts. However,
forming directly the required final shape is preferred as it
eliminates additional production steps.
[0084] The material has the advantage that it is flexible and will
not crumble or stick to other parts, making storing and transport
easier.
[0085] Preferably the noise attenuating has a variable thickness
and or variable area weight over the surface of the material layer.
The variable thickness and or variable area weight allows to
optimise the acoustic performance of the trim part as well as
reducing the weight of the noise attenuating layer by reducing the
thickness of the material in areas where this is suitable without
impairing the overall acoustic performance of the trim part. The
noise attenuating material may also be produced such that there are
areas without noise attenuating material, for example holes in the
noise attenuating trim part.
[0086] Preferably the final noise attenuating material has a shore
A hardness in the range of between 70A and 95A. Preferably the
noise attenuating material may have additionally an E-modulus
between 10 and 80 Mpa. (The E-modulus as measured according to
ISO527-2/5/100 using a test speed of 100 mm/min and a clamping
distance of 80 mm.) Ensuring an optimal softness and flexibility
required for an optimised acoustic layer.
FIGURES
[0087] FIG. 1 is a schematic cross-sectional view of a car with a
car part containing a noise attenuating material layer according to
the invention.
[0088] FIG. 2 shows schematic cross-sectional view of an injection
mold with the noise attenuating material according to the
invention.
[0089] FIG. 3A shows a preferred embodiment of injection molded
noise attenuating material directly molded on top of the surface of
a porous layer.
[0090] FIG. 3B shows a preferred embodiment of injection molded
noise attenuating material directly molded on top of the surface of
a porous layer.
[0091] FIG. 3C shows a preferred embodiment of injection molded
noise attenuating material directly molded on top of the surface of
a porous layer.
[0092] FIG. 3D shows a preferred embodiment of injection molded
noise attenuating material directly molded on top of the surface of
a porous layer.
[0093] FIG. 3E shows a preferred embodiment of injection molded
noise attenuating material directly molded on top of the surface of
a porous layer.
DETAILED DESCRIPTION
[0094] FIG. 1 is schematic cross-sectional view of a car (1). To
attenuate noise coming from the engine bay area and entering the
passenger compartment via the wall between the engine bay area and
the passenger compartment a dash trim part, also called inner dash
trim part or cladding, may be placed against the partition wall
either on the insight of the passenger compartment as shown or the
other way around in the engine bay area, normally called outer dash
trim part. The trim part comprises at least of 2 layers a
decoupling layer (2) facing the car body and the noise attenuating
layer according to the invention (also called barrier or heavy
layer) (3) facing the passenger compartment. Additional layers, not
shown, may be present, for example additional absorbing layers,
carpet or decorative layers preferably placed on the surface of the
noise attenuating facing away from the partitioning wall.
[0095] Such an acoustic trim part might also be placed in other
areas to attenuate vibrational noise, for instance on the main
floor area in the passenger compartment partly under the seat of
the passengers.
[0096] FIG. 2 shows schematic cross-sectional view of an injection
mold (11) and an example of noise attenuating (6).
[0097] The thermoplastic compound is mixed and heated in a unit (7)
before it is fed by low pressure force into the mold tool, for
example by a screw-type plunger (8). The compound enters the mold
hot runner system (9) and is moved by pressure to the injectors
(10), may also be referred to as injector nozzles, and then into
the mold cavity where the noise attenuating (6) is formed under
pressure (F). The molds upper part (4) and a lower part (5) remain
closed during the molding process.
EXAMPLE 1
[0098] Noise attenuating material is mixed comprising 68% of
filler; 19% of component A and 7.0% of component B formed by a mix
of component B1 and B2 in a ratio of 1 to 1.8 and heated ready for
injection into a mold. Other additives as disclosed were added to
obtain 100%.
[0099] A mold is formed from 2 mold halves with a cavity in the
form of the requested noise attenuating part or parts. The mold is
fully closed for the start of the injection. Eventually venting
points are integrated for the escape of trapped air. The injection
can be done by single or multiple injection points.
[0100] The material is injected in the mold and after a predefined
cooling time the mold is opened and the part eventually taken out
of the mold.
[0101] Alternatively, at least one additional layer is introduced
in the mold such that the noise attenuating material can be
injected directly against the surface on predefined areas of the
additional layer or for full coverage. Preferably the additional
layer is only taking in some of the injected material to obtain a
bonding between the surface of the additional layer and the
injected material. Preferably the injected material is not able to
pass through the full thickness of the additional layer to prevent
leaking and stains on the outer surface.
[0102] FIGS. 3A to E are showing different layouts integrating the
noise attenuating material according to the invention.
[0103] FIGS. 3A to 3C shows dual layer trim parts with the noise
attenuating material according to the invention 3, in the form of a
full layer 3, a patch 3a or a full layer partly increased in
thickness due to a recess (or recesses) formed in either the mold
or in the additional layer 2.
[0104] The additional layer can be foam or felt layer in the
different variances as disclosed previously. In case the additional
layer is touching a surface of the car the dual layer product will
function as an acoustic mass spring system with the noise
attenuating material layer working as the mass, barrier or heavy
layer and the additional layer will work as the spring or
decoupling layer.
[0105] A product as such can be placed against a floor or a wall of
the vehicle, like for instance the body in white or the
partitioning wall between passenger compartment and engine bay. The
product formed can be an acoustic trim part or cladding, for
instance the inner or outer dash, the floor or the trunk.
[0106] FIG. 3D is showing the same layers as already described in
FIG. 3A to C. With at least the noise attenuating material layer
(3) and a first additional layer (2), further comprising an
additional carpet system build with a layer 6 being a second
backing layer or optionally an air flow resistive backing layer and
in addition a tufted surface layer (5) alternatively a nonwoven top
layer can be used (not shown), together forming a carpet system.
The noise attenuation layer (3) is shown here as a full covering
layer however also the variant of 3a and 3b can be used here to
further reduce the overall weight and/or to optimise the acoustic
performance of the final trim part. This type of trim parts can be
used for instance for the main floor, the inner dash or the
trunk.
[0107] FIG. 3E shows a classical absorber barrier absorber system
with the barrier made of the noise attenuating material according
to the invention and first and second additional layer (2 and 7)
whereby the top layer (7) might be different than the backing layer
(2). Both layers might be made with foam and or felt and at least
the top layer facing towards the open space is pervious to air,
preferably with an air flow resistance of between 200 and 5000
Nsm.sup.-3, preferably between 500 and 3000 Nsm.sup.3. The noise
attenuating material and the first additional layer (2) will mainly
insulate noise while the additional top layer (7) will in addition
absorb noise.
* * * * *